git ssb

1
const Tree = require('merkle-radix-tree')
2
const Graph = require('ipld-graph-builder')
3
const chunk = require('chunk')
4
const Kernel = require('./kernel.js')
5
const Scheduler = require('./scheduler.js')
6
const DFSchecker = require('./dfsChecker.js')
7
8
module.exports = class Hypervisor {
9
  /**
10
   * The Hypervisor manages the container instances by instantiating them and
11
   * destorying them when possible. It also facilitates localating Containers
12
   * @param {Graph} dag an instance of [ipfs.dag](https://github.com/ipfs/interface-ipfs-core/tree/master/API/dag#dag-api)
13
   * @param {object} state - the starting state
14
   */
15
  constructor (dag, state = {'/': Tree.emptyTreeState}) {
16
    this.graph = new Graph(dag)
17
    this.tree = new Tree({
18
      graph: this.graph,
19
      root: state
20
    })
21
    this.scheduler = new Scheduler()
22
    this.state = state
23
    this._containerTypes = {}
24
    this._nodesToCheck = new Set()
25
26
    this.ROOT_ID = 'zdpuAm6aTdLVMUuiZypxkwtA7sKm7BWERy8MPbaCrFsmiyzxr'
27
    this.CREATION_ID = 0
28
    this.ROUTING_ID = 1
29
    this.MAX_DATA_BYTES = 65533
30
  }
31
32
  /**
33
   * add a potaintail node in the state graph to check for garbage collection
34
   * @param {string} id
35
   */
36
  addNodeToCheck (id) {
37
    this._nodesToCheck.add(id)
38
  }
39
40
  /**
41
   * given a port, this finds the corridsponeding endpoint port of the channel
42
   * @param {object} port
43
   * @returns {Promise}
44
   */
45
  async getDestPort (port) {
46
    if (port.destPort) {
47
      return port.destPort
48
    } else {
49
      const containerState = await this.tree.get(port.destId)
50
      return this.graph.get(containerState, `ports/${port.destName}`)
51
    }
52
  }
53
54
  async send (port, message) {
55
    const id = port.destId
56
    if (id) {
57
      const instance = await this.getInstance(id)
58
      instance.queue(port, message)
59
    } else {
60
      // port is unbound
61
      port.destPort.messages.push(message)
62
    }
63
  }
64
65
  // loads an instance of a container from the state
66
  async _loadInstance (id, state) {
67
    if (!state) {
68
      state = await this.tree.get(id)
69
    }
70
    const container = this._containerTypes[state.type]
71
    let code
72
73
    // checks if the code stored in the state is an array and that the elements
74
    // are merkle link
75
    if (state.code && state.code[0]['/']) {
76
      await this.graph.tree(state.code, 1)
77
      code = state.code.map(a => a['/']).reduce((a, b) => a + b)
78
    } else {
79
      code = state.code
80
    }
81
82
    // create a new kernel instance
83
    const kernel = new Kernel({
84
      hypervisor: this,
85
      state: state,
86
      code: code,
87
      container: container,
88
      id: id
89
    })
90
91
    // save the newly created instance
92
    this.scheduler.update(kernel)
93
    return kernel
94
  }
95
96
  // get a hash from a POJO
97
  _getHashFromObj (obj) {
98
    return this.graph.flush(obj).then(obj => obj['/'])
99
  }
100
101
  /**
102
   * gets an existsing container instances
103
   * @param {string} id - the containers ID
104
   * @returns {Promise}
105
   */
106
  async getInstance (id) {
107
    let instance = this.scheduler.getInstance(id)
108
    if (instance) {
109
      return instance
110
    } else {
111
      const resolve = this.scheduler.lock(id)
112
      const instance = await this._loadInstance(id)
113
      await instance.startup()
114
      resolve(instance)
115
      return instance
116
    }
117
  }
118
119
  /**
120
   * creates an new container instances and save it in the state
121
   * @param {string} type - the type of container to create
122
   * @param {*} code
123
   * @param {array} entryPorts
124
   * @param {object} id
125
   * @param {object} id.nonce
126
   * @param {object} id.parent
127
   * @returns {Promise}
128
   */
129
  async createInstance (message, id = {nonce: 0, parent: null}) {
130
    const idHash = await this._getHashFromObj(id)
131
    const state = {
132
      nonce: [0],
133
      ports: {},
134
      type: message.data.type
135
    }
136
137
    if (message.data.code && message.data.code.length) {
138
      state.code = message.data.code
139
    }
140
141
    // create the container instance
142
    const instance = await this._loadInstance(idHash, state)
143
144
    // send the intialization message
145
    await instance.create(message)
146
147
    if (Object.keys(instance.ports.ports).length || instance.id === this.ROOT_ID) {
148
      if (state.code && state.code.length > this.MAX_DATA_BYTES) {
149
        state.code = chunk(state.code, this.MAX_DATA_BYTES).map(chk => {
150
          return {
151
            '/': chk
152
          }
153
        })
154
      }
155
      // save the container in the state
156
      await this.tree.set(idHash, state)
157
    } else {
158
      this.scheduler.done(idHash)
159
    }
160
161
    return instance
162
  }
163
164
  createChannel () {
165
    const port1 = {
166
      messages: []
167
    }
168
169
    const port2 = {
170
      messages: [],
171
      destPort: port1
172
    }
173
174
    port1.destPort = port2
175
    return [port1, port2]
176
  }
177
178
  /**
179
   * creates a state root starting from a given container and a given number of
180
   * ticks
181
   * @param {Number} ticks the number of ticks at which to create the state root
182
   * @returns {Promise}
183
   */
184
  async createStateRoot (ticks) {
185
    await this.scheduler.wait(ticks)
186
187
    const unlinked = await DFSchecker(this.tree, this._nodesToCheck, (id) => {
188
      return this.ROOT_ID === id
189
    })
190
    for (const id of unlinked) {
191
      await this.tree.delete(id)
192
    }
193
    return this.graph.flush(this.state)
194
  }
195
196
  /**
197
   * regirsters a container with the hypervisor
198
   * @param {Class} Constructor - a Class for instantiating the container
199
   * @param {*} args - any args that the contructor takes
200
   * @param {interger} typeId - the container's type identification ID
201
   */
202
  registerContainer (Constructor, args, typeId = Constructor.typeId) {
203
    this._containerTypes[typeId] = {
204
      Constructor: Constructor,
205
      args: args
206
    }
207
  }
208
}
209